The present invention relates to an eyeglass lens processing apparatus which performs a piercing process on an eyeglass lens in order to attach a rimless frame.
Generally, a piercing (drilling) process on an eyeglass lens, which is performed in order to attach a rimless frame such as so-called two-point frame, is manually performed by a drilling machine. However, recently, an eyeglass lens processing apparatus which can automatically perform the piercing process is suggested (see U.S. Pat. No. 6,790,124 (Japanese Unexamined Patent Application Publication No. 2003-145328))
The piercing process includes a step of forming a through hole, forming a spot-facing hole (non-through hole) and the like. In the processing apparatus, a drill and an end mill having a diameter of about 1 nm are used as a piercing (drilling) tool in consideration of the inner diameter of a hole formed in the eyeglass lens. However, the piercing tool is frangible. More particularly, when forming the spot-facing hole, the depth of the spot-facing hole formed by the piercing tool must be adjusted whenever the piercing tool is replaced with a new piercing tool. This is because the position of the front end of the piercing tool varies in an axial direction due to an individual difference in the length of the piercing tool itself and error generated when attaching the piercing tool to the processing apparatus. A method of adjusting the depth of the spot-facing hole is generally performed using a try and error method. However, this method is laborious and consumes much processing time.